a) 257 cm2
b) 286 cm2
c) 292 cm2
d) 302 cm2
Answer: b
Explanation: Internal radius, r = 4 cm
External radius, R = 5 cm
Total surface area :
$$\eqalign{
& = 2\pi {R^2} + 2\pi {r^2} + \pi \left( {{R^2} – {r^2}} \right) \cr
& = 3\pi {R^2} + \pi {r^2} \cr
& = \left[ {\pi \left( {3 \times 25 + 16} \right)} \right]{\text{ c}}{{\text{m}}^2} \cr
& = \left( {\frac{{22}}{7} \times 91} \right){\text{c}}{{\text{m}}^2} \cr
& = 286{\text{ c}}{{\text{m}}^2} \cr} $$
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